The Squamscott river as you go down Route 101 in Exeter or Route 108 in Newmarket/Newfields has a demanding presence.  I have even seen Skulls  with people rowing up and down the river.  The river flows from Exeter (From where the Exeter river ends at the dam to Great Bay.  I have heard that the best time to take the kayak on that river is to start about 2 hours before high tide leaving on Route 108.  There is a great place to put in a boat.  It has a parking area and even an out house to change or to do last minute duties prior to spending 4 hrs. on the river.  Leaving two hours before will allow the boat to follow the tide up the river, maybe leave sometime to walk and eat in Exeter and then follow the tidal waters to go back to the car.

Here are some internet connections of some interest to this river

This has a great aerial photogragh of the river and contains tidal charts  http://nh.usharbors.com/harbor-guide/squamscott-river

Here is a movie to give advance info on what one sees when traveling down the river from Exeter to Great Bay.   It does not replace actually going up and down the river but it is a great movie.    http://rivermovie.org/

Land use map around the Squamscott river  http://greatbaypartnership.org/mapsquamscott.html